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Good Or Bad Idea? Taking A 350 TBI And 700R4 Trans Out a 1990 Suburban Amd Into A 1984 Suburban

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blackandgold51

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I saw a 1984 Suburban 3 Quarter Ton 4x4 for sale which it has a 454 carb engine and 3 speed transmission. Perso. The body is in not bad shape,just the fron driver side quarter panel is damaged and the vehicle needs good shocks and a good sway bar.

It runs and drives.

However I ha e a 1990 half ton with a 350 fuel iinjected rebuilt along with a solid 700r4 built transmission that can handle 600 horsepower.

Plus its a 4x4.

I want to take the engine and transmission out the 1990 and put into the 1985 3 Quarter ton suburban. The 350 is solid and I don't want to lose it.

Plus sell the 1990 body
 
What's wrong with the 1990? Both are 4x4? Because the trans tunnel is different between 2x and 4x. The 1990 trans should have electric lock-up, so take the whole engine wiring harness and ECU with the engine and trans.

Have you considered swapping the 3/4-ton running gear underneath the 1990 instead?
 
Blue85 said:
What's wrong with the 1990? Both are 4x4? Because the trans tunnel is different between 2x and 4x. The 1990 trans should have electric lock-up, so take the whole engine wiring harness and ECU with the engine and trans.

Have you considered swapping the 3/4-ton running gear underneath the 1990 instead?
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Taking the running gear out of the 3 quarter ton and putting it under the 1990 instead of taking the engine and transmission out of the 1990 and putting it in the 3 quarter ton?

Also for 1 the 1985 body has over 160000 miles while the 1990 has over 300000 miles or more(can't tell exactly because the odometer went out) and the 1985 has the barn doors for simple access the other has a tailgate .plus its a 3 quarter ton frame which may be better than the half ton frame along with the he a y duty parts
 
Sounds like you've swapped in this engine and transmission because it's unlikely you want a 300,000 mile donor. You described body damage on the '84, but didn't mention any issues with the '90, so it sounded like a nicer truck. To make a 1/2-ton Sub a 3/4-ton is basically swapping in 3/4-ton springs and axles, which will come with bigger brakes. You might need the brake MC as well. The driveshaft length will change a little in the back. Generally speaking the most important thing for the build is a body that doesn't need rust repair or paint. You can swap the whole interior from a donor in a day, for example.

For quad shocks, just run 1 set of decent shocks in the longer of the two positions.
 
Blue85 said:
Sounds like you've swapped in this engine and transmission because it's unlikely you want a 300,000 mile donor. You described body damage on the '84, but didn't mention any issues with the '90, so it sounded like a nicer truck. To make a 1/2-ton Sub a 3/4-ton is basically swapping in 3/4-ton springs and axles, which will come with bigger brakes. You might need the brake MC as well. The driveshaft length will change a little in the back. Generally speaking the most important thing for the build is a body that doesn't need rust repair or paint. You can swap the whole interior from a donor in a day, for example.

For quad shocks, just run 1 set of decent shocks in the longer of the two positions.
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No. I haven't change the engine and transmission of the 350 TBI and 700r4 to the from the 1990 to the 1985 3 quarter ton yet. I haven't looked at the vehicle yet in person which I will this Friday. I saw it on Craigslist and talked to the owner on phone. They said their moving out of town soon and wants to sell the vehicle before the move.

The main thing I like about the vehicle is that it has the rear barn doors and its a three quarter ton along with being a 4x4.

However the 454 with a 3 speed is a downfall because it has power but bad fuel mileage which is why I rather take those out and use the 1990 as a donor.

But like the other poster said. Therea not much between a 3 quarter ton and half ton and like you said its better to go the other away around by using the 1985 as a donor instead
 
Are you sure there's a front differential under there? It sits kind of low for a 4x4 2500.
 
Blue85 said:
Are you sure there's a front differential under there? It sits kind of low for a 4x4 2500.
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" 1985 suburban 2500 series 454 engine..needs minor work..heater still work. The engine is very strong..although it's old it still runs good. In need of a sway bar and shocks..only 3 dents in body..asking for $1500 but will settle for no less than $1200"
 
Shocks have nothing to do with ride height.
  • "heater still work" why bring this up? Is it the only thing that still works?
  • "only 3 dents" - well one is half of a fender, so what else are you down-playing?
  • "asking for $1500 but will settle for no less than $1200". Sorry, genius, nobody is offering more than $1200 now.
So you have to look at it in person. Just because somebody checked a box for 4x4 in the listing won't make it a 4x4.
 
It could be an optical illusion, but it looks like the front tires are smaller than the rear, which is more likely to happen on a 2x4.
 
Blue85 said:
Shocks have nothing to do with ride height.
  • "heater still work" why bring this up? Is it the only thing that still works?
  • "only 3 dents" - well one is half of a fender, so what else are you down-playing?
  • "asking for $1500 but will settle for no less than $1200". Sorry, genius, nobody is offering more than $1200 now.
So you have to look at it in person. Just because somebody checked a box for 4x4 in the listing won't make it a 4x4.
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Plus the person thinks these things are rare. Which there not really rare. I still see these suburban sometimes around. Not often but not not to were you can see them once or twice a year
 
You can see the IFS chicken wings hanging down in the front shot. 2WD all the way.


Moreover, as Martin loves to say...

82355 said:
You are correct. GM did not install a big block in ANY 4x4 rigs from 1973-1980. In 1981-1987, the only way to get a big block in a 4x4 was the K30. No 4x4 Suburban came with a big block from 1973-1991, and no Blazer ever came with a big block.

Martin
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82355 said:
No 4x4 Suburbans from 1973-1991 got a big block.

Martin
Click to expand...

82355 said:
The big block was not available in 4x4 Suburbans. So if it had a 454 it would be 2wd, and would be far from perfect.

Martin
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:thumb:
 
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